Articles for use at low temperatures



Patented June 26, 1945 Russell Franks, Niagara Falls, N. Y.,- assignorto Electro Metallurgical Company, a corporation of West Virginia NoDrawing. Application January 16, 1943,

Serial N0. 472,597

9 Claims. (01. 75-123) This invention relates to'steel articles for useat low temperatures.

A demand exists in industry for steels forl'use in the fabrication ofapparatus for use at lowtemperatures, for example for refrigeratingequipment or for apparatus used in the handling of liquefied gases suchas oxygen, nitrogen, or

air. Many steelswhich have excellent strength and toughness at normalatmospheric temperatures become brittle when exposed to temperaturesbelow zero on the centigrade scale, and few ferrous materials have therequisite toughness to withstand shock at the exceedingly lowtemperatures encountered in handling liquefied air or oxygen. Stainlesssteels of the type containing about 18% chromium anrk8% nickel haveexcellent toughness even at temperatures in the neighborhood of l83 C.,and have been widely used in liquid oxygen equipment, but these steelsare relatively expensive. Although nonferrous metals 'and alloys are notas susceptible as ferrous materials to loss of toughness at lowtemperatures, in general, their strength is not great.

It is the chief object of'this invention to provide articles for use atlow temperatures which articles -are composed of steel which possessesthe gbility to withstand shock at Very low temperaures.

Th invention by means of which this object is achieved is based on thediscovery that austeniti'c manganese steels which contain substantialproportions of manganese within certain narrow, critical limits and aminor proportion of at least one austenite-stabilizing element selectedfrom the group consisting of nickel and copper, with or without chromiumin a proportion up to 16%. have the ability to withstand shock atsub-zero temperatures The invention comprises articles for use at low.temperatures composed of such steels.

More specifically, the invention comprises articles for use at lowtemperatures, which articles are composed of steel containing about 15%to 20% manganese, 0.2% to 8% of at least one austenite-stabilizingelement selected from the group 45 consisting of nickel and copper, upto about 16% chromium and the remainder chiefly iron. Preferably, thesteel contains both nickel and copper. Ii nickel alone is used, thesteelshould contain about 0.5% to (preferably 1% to 5%) of this element.If copper alone is used, the steel, should contain about 0.25% to 2% ofthis element, but if both copper and nickel are used, the copper contentmay be as high as 3%. Ordinarily, the presence of more than 3% of coppershould be avoided because of the detrimental effect of copper on the hotworking properties of the steel.

, The presence of chromium in the steel not only improves its toughnessat low temperatures but also enhances its resistance to corrosion. Wherecorrosion-resistance is not important, chromium may be omittedaltogether, but in such case the sum of the nickel and copper contentshould be at least 4%, and preferably at least 5%, of the steel tosecurethe desired low temperature toughness. Where resistance merely toprogressive rusting is desired, the steel should contain about 0.25% to8%, preferably 1% to 4%, chromium. In steels containing chromium in thisrange, the sum of the nickel and copper contents need not be as high aswhen chromium is not present in the steel. Where a high degree ofresistance to corrosion is required of the articles of the invention inaddition to low temperature toughness, the

steel of which they are composed should contain about 8% to 16%chromium, and in such case for the greatest degree of toughness at lowtempera- 20 ture, the steel shouldcontain about 012% to 3% nickel orabout 0.2% to 2.25% copper or both nickel and copper. A preferred lowerlimit for nickel or copper or both is about 0.25%. Generally, bestresults are obtained in all of these steels if nickel or both nickel andcopper are present, but in the higher chromium steels a small proportionof either will suflice.

The carbon content of the steel of which the articles of the inventionare composed should not exceed about 0.5% and is preferably about 0.01%

to 0.35%. Nitrogen in a proportion up to about 0.15% and phosphorusup'to about 0.4% (pref erably not more than about 0.2%) may be presentin the steel, nitrogen in particular having a beneficial effect on itstoughness. There will also ordinarily be normal percentages of residualdeoxidizers, scavengers and grain refiners such as silicon and calciumpresent in the steel.

The articles of the invention should be an-' I .nealed before-exposureto low temperatures, suitably by heating them at a temperature aboveabout 900 C. and then rapidly cooling them in water or air. r

The toughness atlow temperature of aus'tenitic man anese steelscontainin various amountsof nickel, copper, and chromium is illustratedby the test data set forth in Table I. Inrthis table the impactresistance at room temperature and w at 183 C. of the steels asdetermined in the standard Izod impact test is given in foot pounds. Thespecimens tested at l83 C. were cooled to that temperature by immersingthem in liquid air for one-half to one hour and then were quicklytransferred to the impact machine and tested.

Before testing, all specimens were annealed by heating them for ten totwenty minutes at 1000 C. to 1050 C(and then cooling them in air.

Table I Composition (remainder iron) Impact resistance Percent PercentPercent Percent Percent Room Mn Ni Cu Cr C temp.

14 Nil Nil Nil 0. 30 8 0. 75 16.5 Nil Nil Nil 0.20 32 '3 18 Nil Nil Nil0.30 65 2 17 2.0 Nil Nil 0.29 96 16 16 4.6 Nil Nil 0.30 94 30 17 2 1 Ni]0.20 103 20 16.5 2 2 Nil 0.10 90 46 16 2 2 Nil 0.40 70 32 17 3 1 Ni]0.10 107 41 16 2 1 3 0.2) 102 28 17 2 2 3 0.10 97 63 17. 5 2 Nil 5. 070. 2) 93 42 16. a 0. 54 Nil 12. 9 0. 15 105) 60 16.6 1.10 Nil 13.2 0.15100 07 16. 2 2. 10 N 11 13. 2 0. 14 100 90 16.5 Nil 0.75 12.8 0.13 10067 I 16.6 0.58 0.64 12.9 0.13 100 64 16.3 1.10 0.60 13.0 0.12 98 78 Thedata in Table I show the drop in toughness of the plain high manganesesteel at low temperature and that the addition of copper or nickel orboth markedly improves the toughness of high manganese steel at lowtemperature. Even further improvement is shown by steels containingchromium inaddition to nickel or copper or both.

Tensile test data set forth in Table II below demonstrate that theducitility or high manganese steel, as measured by the percentageelongation in a two inch gauge length, is enhanced by the presence ofone or both of the elements nickel and copper, with or without chromium.

Table II Composition (remainder iron) Yield Tensile 5:; Per- Per- Per-Per Perg g g ei. in cent cent cent cent cent 2" Mn Ni Cu Cr C 14 N11 N11N11 0. 30 38, 500 110, 300 14 16. 5 N11 N11 N i] 20 36, 100 127, 300 2417 2 Nil Ni] 0.29 35,000 ,000 60 17 4. 5 N11 N11 0. 28 31, 800 112, 90062 10. 5 2 1 N11 0. 500 111, 300 59 16. 5 2 2 N11 0. 10 28, 000 100, 70062 16 2 2 N11 0. 40 37, 100 1 000 69 16 2 1 3 0. 35, 100 120, 400 I 6116 2 2 3 0. 13 600 136, 500 65 17. 5 2 N11 5. 07 0. 20 40, 700 120, 00053 16. 5 N11 0. 75 12. 8 0. 13 1110 123, 000 63 16. 5 0. 54 N11 12. 90.12 36, 000 120, 500 63 16. 5 1. 1 N11 13. 2 0. 15 38, 500 124, 500 6710. 3 1. 1 0. 6 l3 0. 12 35, 000 08, 000 63 16. 2 2. 1 N11 13. 2 0. 14 v36, 000 110, 000 63 1 6. 5 2 1. 5 12 0.10 000 101, 500 58 The test datashown in Table II were obtained on standard tensile'test specimens atroom temperature, the yield strength at 0.2% offset being determined inaccordance with United States Navy Department specification No. 47521.Inthe table yield strength p. s. i. represents the yield strength intension measured at 0.2% permanent,

set in pounds per square inch; "tensile strength less steel weldingrodscontaining about 5% to 30% chromium and 5% to 30% nickel, for instance,using rods containing 18% chromium and 8% nickel or 24% chromium and 12%nickel or 25% chromium and 20% nickel.

.which article is composed of a steel containing about 15% to 20%manganese to render said steel austenitic, about 0.2% to 8% of at leastone austenite-stabilizing element selected from the group consisting ofnickel and copper, thecopper content not exceeding about 3% of thesteel, 0.01% to 0.5% carbon and the remainder iron and incidentalelements having to substantial adverse eflect on the low temperaturetoughness of said steel.

2. A steel article foruse at low temperatures, which article is composedof a steel containing about 15% to 20% manganese to render said steelaustenitic, about 0.2% to 8% of at least one austenite-stabilizingelement selected from the group consisting of nickel and copper, thecopper content not exceeding about 3% of the steel, up to about 16%chromium, 0.01% to 0.5% carbon and the remainder substantially all iron.

3. A steel article for use at low temperatures,

which article is composed of a steel containing about 15% to 20%manganese, about 0.5% to 5% nickel, 0.01% to 0.5% carbon and theremainder substantially all iron.

4. A steel article for use at low temperatures. which article iscomposed of a steel containing about 15% to 20% manganese, about 0.2% to8% of at least one austenite-stabilizing element selected from the groupconsisting of nickel and copper, the copper content not exceeding 3% ofthe steel, about 0.25% to 8% chromium, 0.01% to 0.5% carbon and theremainder substantially all iron.

5. A steel article for use at low temperatures, which article iscomposed of a steel containing about15% to 20% manganese, 1% to 5%nickel,

0.25% to 2% copper, 0.25% to 8% chromium, 0.01% to 0.5% carbon and theremainder substantially all iron.

6. A steel article for use at low temperatures, which article iscomposed of a steel containing about 15% to 20% manganese, 1% to 5%nickel, 0.25% to 2% copper, 1% to 4% chromium, 0.01% to 0.35% carbon andthe remainder substantially all iron.

'7. A steel article for use at low temperatures, which article iscomposed of a steel containing about 15% to 20% manganese, 0.2% to 3%nickel, 0.2% to 2.25% copper, 8% to 16% chromium, 0.01% to 0.5% carbonand the remainder sub.-

- stantially all iron.

8. A steel article resistant to progressive rusting which in its normaluse is required to withstand shock at temperatures below zero on thecentigrade scale, which article is composed of a steel containing about15% to 20% manganese, 0.25% to 5% nickel, 0.25% to 2% copper, 0.25% to8% chromium, 0.01% to 0.5% carbon, the remainder substantially all iron.

9. A corrosion-resistant steel article which in its normal use isrequired to withstand shock at temperatures below zero on thecentrigrade scale, which article is composed of a steel containing aboutto 20% manganese, 0.25% to 3% nickel, 0.25% to 2.25% copper,- 8% to 16%chromium, 0.01% to 0.5% carbon, the remainder substantially all iron.

- RUSSELL FRANKS.

CERTIFICATE OF CORRECTION. Patent No. 2,578,992. June 26, 19h5.

RUSSELL FRANKS.

It is hereby certified that error appears in the printed specificationof the above numb ered patent requiring correction as follows: Page 2,first column, line 51 for "d i ti lity" read "ductility"; line 6'5, for"pound" read -pounds-; and second column, line 15, for "having to" read-'-having no-; and that the said Letters Patent should be read with thiscorrection therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 21d day of October, A. D. 1914.5.

Leslie Frazer (Seal) First Assistant Commissioner of Patents.

